Method of producing and refining alloys



Patented May 5,1931

HARRY F. PORTER, F TRENTON, NEW JERSEY METHOD OF PRODUCING AND REFININGALLOYS No Drawing. Original application filed January 20, 1927, SerialNo. 162,245. Divided and this application filed September 28, 1928.

16 In my researches, I have found that a magnetic alloy may be made ofcopper, nickel and iron within the limits of Per cent Copper; 3-10 20Nickel 35-55 Iron 35-55 which incertain fields of application iselectrically and magnetically superior to known magnetizable substancesand processes the additional mechanical advantage of being easilyworked, as is hereinafter more fully described.

The alloy per se and electro-magnetic devices utilizing it are claimedin my co-pend ing application Serial No. 162,245 filed January 20, 1927,of which this application is a division.

The preferred method of making this ternary alloy consists of placing aquantity of manganese or manganese and magnesium in the bottom of thesilica or quartz crucible 'of an induction furnace and superimposingupon it the proper proportion of copper. In

lieu of this arrangement, an alloy of copper 40 and manganese, or ofcopper and magnesium, or of copper, manganese andmagnesium, is emplo ed.In any case, the iron and nickel, prefera ly in the form of sheetsalter.- nately arranged, are placed above the copper mixture of alloy sothat the latter, which melts first, in effect forms a solvent in whichthe iron and nickel diss0lve.- The downward movement of these meltingmetals and the currents induced by the primary winding of the furnacecause a. stirring action which re- Serial No. 309,087.

the nickel and also cleoxidizes it. The iron should be of high purity,containing from but .01% to 03% carbon. The copper, which-may be of theusual commercial varie ties, is of high oxygen content and refines fromthe iron the small traces of carbon that may be present. By arrangingthe materials in the furnace as described, the melting and refiningoperations proceed simultaneously. The alloy should be poured soon afterthe entire mass has become molten; otherwise gases are formed whichproduce porous bars or castings.

An important advantage of my refining operation is that metalsobtainable commercially, may be utilized in such operation, therebygreatly reducing the cost thereof. Commercial copper generally containsan appreciable amount of oxygen in the form of copper oxide, whilecommercial ingot iron necessarily contains a small amount of carbon; anamount too high, however, for use in highly sensitive magnetic alloys.lVhen the copper in the bottom of the crucible has melted, and as theiron which is of greater Weight, gradually dissolves and settles in thecopper solvent, the oxygen present in the copper effects reduction ofthe carbon in the iron. Cold copper has higher specific gravity thancold iron, but when molten the action is as described above. By suchmethod, it is possible to utilize commercial ingot iron instead ofelectrolytic iron, which although more expensive, has been previouslyused to a great extentfor highly sensitive magnetic alloysr For thecombination of 46 570 nickel, 46 iron and the balance of copper, exceptfor small amounts of manganese, magnesium and traces of the usualimpurities, the melting point of the alloy is about 10.

1300 centigrade-and the time of melting a charge depends, of course,upon the amount of material, and other variables.

I The alloy may be cast in various shapes, by the use of cast iron orsand moulds and thereafter machined. After all of the mechanicaloperations have been performed, the castings are annealedin a reducingor neutral atmosphere, free from all traces of carbon, sulphur oroxygen, at temperatures ranging from 900 to 1200 centigrade, the time ofholding and temperature being dependent on the thickness of the pieceand also the desired magnetic characteristics. The metal beforeannealing is, to all practical purposes, non-magnetic.

The castings may be annealed in air if the precaution is taken to coverthem with some substance such as iron borings, to remove impurities fromthe furnace gases before they come in contact with the casting. Further,during the cooling down in the open air, a partial vacuum is produced,sucking in air, which, except for the presence of the filter, as of ironborings, would oxidize the castings. As a matter of fact, the resultsproduced by surrounding the casting with iron filings and annealingin'air are fully as satisfactory as those produced by annealing in anatmosphere of hydrogen, which is considerably more expensive than theiron filing anneal. The hydrogen anneal is very commonly used for highlysensitive magnetic metals, or alloys having no copper in theircomposition. In general, the higher the temperature at which theannealing is performed within the range given, the less the timerequired to attain the desired obj ective.

The magnetic characteristics of the alloy are such that when a castingof the metal is used as a core or other magnetic element inelectro-magnetic devices and the like, as-

transformers, alternating current relays, its performance comparesfavorably with a laminated core of the usual known magnetic alloys, assilicon-steel.

Instead of casting the metal in molds substantially of the shape andsize of the finished productit may be poured in flat slabs similar-tothe practice employed with nonferrous metals prior to rolling. The barsor slabs are very malleable, and may be either hot or cold rolled,preferably cold rolled so as to reduce to a minimum the absorption ofcarbon, oxygen or sulphur during the rollmg, inasmuch as any of theseimpurities are detrimental to the final desired magnetic qualities ofthe alloy. It is almost impossible to safeguard against this poisoningof the metal during the much more involved and expensive hot rollingprocess which is employed with the known magnetic substances. The coldrolling also eifects a change in the internal structure of the alloysuch that an examination under the microscope of a cross-section of thecold rolled metal reveals a series of minute, finely separated laminae.

This undoubtedly is explanatory of the low, eddy current losses of thealloy when cold rolled in the form of strips since each lamination orstrip is in itself a plurality of thinner laminations. A similarcondition results to a lesser degree if a castingof the material issubjected to a slight rolling consisting of a few passes.

After all mechanical operations have been completed, the strips areannealed as previously described. The tendency of light strips to sticktogether during the annealing process, if stacked and subjected totemperatures in excess of 925 C. may be mini mized by giving the stripsa light surface oxidation prior to annealing. When annealed in areducing atmosphere the material assumes a high lustre and when airannealed takes on an oxide coating desirable for transformer or otherconstruction in which a core is built of a pile of laminations.

The alloy may also be poured in round ingots, which are readily drawninto a wire which in turn may be drawn downv to the finest sizes. Afterannealing, the wire may be insulated and employed in circuits, as

radio frequency circuits, wherein high ermeability and low losses atfeeble inductions are desirable. If cold drawn, the rod or wire isstriated, and is, in effect, a bundle of veay fine, substantiallyparallel wires or ro s.

The magnetic properties of the alloy render it particularly useful inelectro-ma netic devices involved in the transmission 0 currents ofsound frequency, such as for example audio-transformers and impedances,having amagnetic member or members subjected to an alternating fluxwhose frequency may vary from 10 to 10,000 cycles per second,superimposed upon a relatively large biasing magneto-motive force.

What I claim is:

1. The method of producing a magnetic alloy which comprises melting apredetermined amount of copper containing copper oxide to form asolvent, melting and issolving predetermined amounts of mckel and ironin said solvent, and efl'ecting reduction of carbon in said alloy by thecopper oxide. v

2. The method of producing a magnetic alloy which comprises melting apredetermined amount of commercial copper containing copper oxide toform a solvent, melting and dissolving predetermined amounts of nickeland commercial ingo. iron in said solvent, and effecting reduction ofcarbon in said iron by the copper oxide.

3. The method of simultaneously producing and refining acopper-nickel-iron alloy which comprises melting by induced electriccurrents a predetermined amount of copper having relatively high oxygencontent, melting and dissolving a predetermined amount of nickel andcommercial iron in said melt, efiecting reduction of carbon in said ironby the oxygen content of the copper, and efiecting a stirring motion ofsaid solution to insure uniformity thereof by said induced currents.

4. The method of producing and refining a copper-nickel-iron alloy whichcomprises placing copper containing appreciable oxygen content in thebottom of a crucible, superimposing nickel, and iron containing lowcarbon content, on said copper, melting said copper to form a solvent,melting and dissolving the nickel and iron in said solvent, andeffecting reduction of the carbon content of the iron as the heaviermetals melt and commingle with said solvent.

HARRY F. PORTER.

